Nanotube electronics templated self-assembly

ABSTRACT

A fabricated substrate has at least one plurality of posts. The plurality is fabricated such that the two posts are located at a predetermined distance from one another. The substrate is exposed to a fluid matrix containing functionalized carbon nanotubes. The functionalized carbon nanotubes preferentially adhere to the plurality of posts rather than the remainder of the substrate. A connection between posts of the at least one plurality of posts is induced by adhering one end of the functionalized nanotube to one post and a second end of the functionalized carbon nanotube to a second post.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of, and claims the benefit of priorityof, U.S. patent application Ser. No. 13/897,480, filed May 20, 2013;which is a divisional of, and claims the benefit of priority of, U.S.patent application Ser. No. 12/874,319, filed Sep. 2, 2010; all of whichare related to, and claim the benefit of priority of, provisional U.S.patent application Ser. No. 61/258,375, filed Nov. 5, 2009, entitled“Nanotube Electronics Templated Self-Assembly”; all of theaforementioned applications are incorporated herein by reference.

BACKGROUND INFORMATION

1. Field

The present disclosure relates generally to methods and systems forproduction of electronic devices, and devices produced therefrom. Morespecifically, the present disclosure relates to methods and systems forproduction of circuits containing nanotubes.

2. Background

Modern processor chip designs often include one or more caches on thesame integrated circuit chip as the processor, and in some cases includemultiple processors on a single integrated circuit chip. Despite theenormous improvement in speed obtained from integrated circuitry, thedemand for even faster computer systems has continued. With this demandcomes a need for even further size reduction in the logic circuitrywithin an integrated circuit chip.

A typical integrated circuit chip is constructed in multiple layers.Many active and passive elements are formed on a substrate (usuallysilicon). A dielectric layer is placed over the elements, and multipleconductive layers, each separated by another dielectric layer, areformed over the elements. The conductive layers carry power and groundpotentials, as well as numerous signal interconnects running amongactive elements. Each conductive layer comprises multiple discreteconductors, often running substantially in parallel. Conductiveinterconnects between conductive layers, or between a conductive layerand an active or passive element, are formed as holes in the dielectriclayers, called vias, into which a conductive metal, such as aluminum orcopper, is introduced.

The number of active elements in a typical processor dictates a verylarge number of interconnections, and since these must be packagedwithin a small area, the size of individual interconnections is limited.Conductors, whether in the conductive layer or the via betweenconductive layers, have a small, finite resistance, which grows as thecross-sectional area of the conductor shrinks. Increasing the number oflogic elements on a chip requires a larger number of conductors, whichin turn reduces the amount of space available for each individualconductor. If all other design parameters remain the same, this has theeffect of increasing the resistances of the individual conductors.

Recently, carbon nanotubes have been used to form conductive pathways inintegrated circuits. Carbon nanotubes are cylindrically structuredcarbon allotropes composed entirely of sp²-hybridized bonding betweencarbon atoms. A single walled carbon nanotube is conceptually aone-atom-thick layer of graphene wrapped into a seamless cylinder.

Manufacturing of carbon nanotube-based electronics requires thepositioning of each individual nanotube, which is prohibitive in termsof time and cost. While carbon nanotube-based electronics can befabricated, individual nanotubes must be directly placed to create thecarbon nanotube-based electronics. The direct placement of nanotubesrequires an atomic force microscopy tip or similar microscope tip toposition each of the nanotubes to form each electrical connection. Therequired time and cost of manually positioning each of the nanotubes toform each electrical connection is prohibitive of production scalemanufacturing of carbon nanotube-based electronics.

Therefore, it would be advantageous to have a method and apparatus thattakes into account at least one of the issues discussed above, as wellas possibly other issues.

SUMMARY

An embodiment of the present disclosure provides methods and systems forproduction of nanotube-enabled circuits that do not rely on manualpositioning of the nanotubes. Carbon nanotubes self-assemble on ametal-templated surface to form electrical connections includingsemiconducting connections that define a circuit.

A fabricated substrate has at least one plurality of posts. Theplurality is fabricated such that the centers of two posts are locatedat a predetermined distance from one another.

Due to the available bond sites on the carbon atoms along the end of ananotube, or due to the increased energy of the carbon bonds whenstretched under curvature in two dimensions, functional groupspreferentially adhere to distal ends of the carbon nanotube. Therelative concentration of functional groups at the distal ends offunctionalized carbon nanotubes creates a concentration of electricalcharges.

The substrate is exposed to a fluid matrix containing functionalizedcarbon nanotubes. The ends of the functionalized carbon nanotubespreferentially adhere to the plurality of posts rather than theremainder of the substrate. A connection between posts of the at leastone plurality of posts is induced by adhering a second end of thefunctionalized carbon nanotube to a second one of the at least oneplurality of posts.

The lengths and chiralities of the functionalized carbon nanotubes arepreselected. The length of the functionalized carbon nanotubes matchesthe predetermined distance between the centers of posts of the pluralityof posts. The chirality of the functionalized carbon nanotubes isselected to impart the desired electrical properties to the createdcircuit.

Carbon nanotubes are cylindrically structured carbon allotropes composedentirely of sp²-hybridized bonding between carbon atoms. The chiralityof the carbon nanotubes is denoted by a pair of indices (n, m). Thevalues of n and m determine the chirality, or “twist” of the nanotube.The chirality, in turn, affects the conductance of the nanotube, itsdensity, its lattice structure, and other properties. For a given (n, m)nanotube, if n=m, that is, the carbon nanotube has an “armchair”chirality, the carbon nanotube is conducting. If n−m is a multiple ofthree, then the nanotube is semiconducting with zero band gap such thatthe nanotube is considered semi-metallic. Otherwise, the nanotube is amoderate semiconductor. The band gap of a semiconducting carbon nanotubeis determined uniquely by the chiral indices (n, m).

An embodiment of the present disclosure provides a method for assemblingcarbon nanotube electronics. A substrate is fabricated, wherein thesubstrate has at least one plurality of posts, the at least oneplurality of posts being fabricated at a predetermined distance from oneanother. The substrate is then exposed to a fluid matrix containingfunctionalized carbon nanotubes. A first end of the functionalizedcarbon nanotube adheres to a first one of the at least one plurality ofposts. A second end of the functionalized carbon nanotube adheres to asecond one of the at least one plurality of posts, wherein a connectionis formed between posts of the at least one plurality of posts.

An embodiment of the present disclosure provides a system for assemblingcarbon nanotube electronics. The system comprises a substrate, whereinthe substrate has at least one plurality of posts, the at least oneplurality of posts being fabricated at a predetermined distance from oneanother. The system also comprises a fluid matrix containingfunctionalized carbon nanotubes, wherein the substrate is exposed to thefluid matrix. Agitation of the fluid matrix adheres a first end of atleast one of the functionalized carbon nanotubes to a first one of theat least one plurality of posts, and induces a connection between postsof the at least one plurality of posts by adhering a second end of theat least one of the functionalized carbon nanotube, to a second one ofthe at least one plurality of posts.

The features, functions, and advantages can be achieved independently invarious embodiments of the present disclosure, or may be combined in yetother embodiments in which further details can be seen with reference tothe following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the advantageousembodiments are set forth in the appended claims. The advantageousembodiments, however, as well as a preferred mode of use, furtherobjectives and advantages thereof, will best be understood by referenceto the following detailed description of an advantageous embodiment ofthe present disclosure when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a carbon nanotube electronics assembly environment depicted inaccordance with an advantageous embodiment;

FIG. 2 is a graphene sheet depicting several vectors along which asingle walled carbon nanotube can be created in accordance with anadvantageous embodiment;

FIG. 3 is a carbon nanotube that has been exposed to a fluid containingfunctional groups in accordance with an advantageous embodiment;

FIG. 4 is a fabrication technique of a printed circuit board inaccordance with an advantageous embodiment;

FIG. 5 is a fabrication technique of a printed circuit board inaccordance with an advantageous embodiment;

FIG. 6 is a fabrication technique of a printed circuit board inaccordance with an advantageous embodiment;

FIG. 7 is a functionalized carbon nanotube bath for creating pathways inaccordance with an advantageous embodiment;

FIG. 8 is a completed circuit having a carbon nanotube pathway inaccordance with an advantageous embodiment;

FIG. 9 is a flowchart of a method for assembling carbon nanotubeelectronics in accordance with an advantageous embodiment; and

FIG. 10 is a flowchart of the processing steps for the self-assembly ofa carbon nanotube electronic circuit in accordance with an advantageousembodiment.

DETAILED DESCRIPTION

The different advantageous embodiments provide a method and system forproduction of nanotube-enabled circuits that do not rely on manualpositioning of the nanotubes. Carbon nanotubes self-assemble on ametallic templated surface to form electrical connections. Theseelectrical connections include, for example, without limitation,semiconducting connections that define a circuit.

A substrate has at least one plurality of posts. The plurality of postsis fabricated such that the center of two posts are located at apredetermined distance from one another.

Other pluralities of posts might be fabricated at other predetermineddistances.

The substrate is exposed to a fluid matrix containing functionalizedcarbon nanotubes. The ends of the functionalized carbon nanotubespreferentially adhere to the plurality of posts rather than theremainder of the substrate. A connection between posts of the at leastone plurality of posts is induced by adhering a second end of thefunctionalized carbon nanotube to a second one of the at least oneplurality of posts.

The lengths and chiralities of the functionalized carbon nanotubes arepreselected. The length of the functionalized carbon nanotubes matchesthe predetermined distance between the centers of the posts of theplurality of posts. The chirality of the functionalized carbon nanotubesis selected to impart the desired electrical properties to the createdcircuit.

With reference now to FIG. 1, carbon nanotube assembly environment isdepicted in accordance with an advantageous embodiment. Carbon nanotubeassembly environment 100 is an exemplary environment in which carbonnanotube electronics 102 may be fabricated. In these examples,Fabrication system 104 is used to fabricate carbon nanotube electronics102.

In the illustrative example fabrication system 104 comprises fluidmatrix 106 and functionalized carbon nanotubes 108. Fluid matrix 106 isa matrix capable of suspending functionalized carbon nanotubes 108 insolution, without dissolving functionalized carbon nanotubes 108. Fluidmatrix 106 acts as a carrier system for delivering and suspendingfunctionalized carbon nanotubes 108 during assembly of carbon nanotubeelectronics 102. In one advantageous embodiment, fluid matrix 106 is anaqueous solution.

Functionalized carbon nanotubes 108 are carbon nanotubes havingfunctional groups attached thereto. Carbon nanotubes are cylindricallystructured carbon allotropes composed entirely of sp²-hybridized bondingbetween carbon atoms. Functionalized carbon nanotubes 108 are formed byexposing carbon nanotubes to a source of functional groups underfavorable reaction conditions.

Due to the available bond sites on the carbon atoms along the end of ananotube, or due to the increased energy of the carbon bonds whenstretched under curvature in two dimensions, functional groupspreferentially adhere to distal ends of the carbon nanotube. Therelative concentration of functional groups at the distal ends offunctionalized carbon nanotubes 108 creates a concentration ofelectrical charges.

Carbon nanotube electronics 102 is a chip, circuit board, or otherelectronic device that includes circuits, pathways, or electricalconnections formed from carbon nanotubes. Carbon nanotube electronics102 includes posts 110 and 112. Posts 110 and 112 are points on carbonnanotube electronics 102 that are to be connected by a carbon nanotube.Posts 110 and 112 are fabricated such that the centers of the two postsare located at a predetermined distance from one another.

The lengths and chiralities of functionalized carbon nanotubes 108 arepreselected. The length of functionalized carbon nanotubes 108 matchesthe predetermined distance between the centers of posts of posts 110 and112. The chirality of the functionalized carbon nanotubes is selected toimpart desired electrical properties to carbon nanotube electronics 102.

Carbon nanotube electronics 102 is exposed to fluid matrix 106. Uponexposure, an end of the functionalized carbon nanotubes 108preferentially adheres to the plurality of posts rather than theremainder of the substrate. A connection between posts of the at leastone plurality of posts is induced by adhering a second end of thefunctionalized carbon nanotube to a second one of the at least oneplurality of posts.

The illustration of carbon nanotube assembly environment 100 in FIG. 1is not meant to imply physical or architectural limitations to themanner in which different advantageous embodiments may be implemented.Other components in addition to, and/or in place of, the onesillustrated may be used. Some components may be unnecessary in someadvantageous embodiments. Also, the blocks are presented to illustratesome functional components. One or more of these blocks may be combinedand/or divided into different blocks when implemented in differentadvantageous embodiments.

Referring now to FIG. 2, a graphene sheet is shown depicting severalvectors along which a single walled carbon nanotube can be created,according to an advantageous embodiment. Graphene sheet 200 isconceptually an unrolled single walled carbon nanotube showing thevarious chiralities that can be formed.

Carbon nanotubes are cylindrically structured carbon allotropes composedentirely of sp²-hybridized bonding between carbon atoms. A single walledcarbon nanotube is conceptually a one-atom-thick layer of graphenewrapped into a seamless cylinder. The chirality of the wrapped graphenesheet is wrapped in the chiral vector, denoted by a pair of indices (n,m). The integers n and m denote the number of unit vectors along twodirections in the honeycomb crystal lattice of graphene. The values of nand m determine the chirality, or “twist” of the nanotube. Thechirality, in turn, affects the conductance of the nanotube, itsdensity, its lattice structure, and other properties.

Vector 210 is represented by an indices of (n, 0). Vectors having an “m”value equal to zero (0) are said to have a “zigzag” pattern that isnon-chiral. Vector 212 is represented by an indices of (n, n), that is,the “n” and “m” values are equal. Vector 212 having an “n” value equalto the “m” is said to have an “armchair” pattern that is non-chiral.Vector 214 is represented by an indices of (n, m), wherein the “n” and“m” values are not equal.

The different chiral structures of carbon nanotubes strongly affect theelectrical properties of the nanotube. For a given (n, m) nanotube, ifn=m, that is, the carbon nanotube has an “armchair” chirality, thecarbon nanotube is conducting. If n−m is a multiple of three, then thenanotube is semiconducting with zero band gap such that the nanotube isconsidered semi-metallic. Otherwise, the nanotube is a moderatesemiconductor. The band gap of a semiconducting carbon nanotube isdetermined uniquely by the chiral indices (n, m).

Referring now to FIG. 3, a carbon nanotube that has been exposed to afluid containing functional groups is shown in accordance with anadvantageous embodiment. Carbon nanotube 310 is a carbon nanotube havinga chirality such described in FIG. 2.

Functional groups 312 preferentially attract to, and concentrate at, thedistal ends of carbon nanotube 310. Functional groups 312 are chemicalfunctional groups capable of adhering to the surface and ends of carbonnanotube 310. In one advantageous embodiment, functional groups 312 arecarboxylic acid functional groups.

Due to the available bond sites on the carbon atoms along the end of ananotube, or due to the increased energy of the carbon bonds whenstretched under curvature in two dimensions, functional groups 312preferentially adhere to distal ends 314 and 316 of carbon nanotube 310.The relative concentration of functional groups at distal ends 314 and316 of carbon nanotube 310 creates a concentration of electricalcharges.

Carbon nanotube 310 is pictured with “open” ends. Nanotubes with openends will experience functionalization preferentially along their ends,due to the available bond sites at the carbons along the edge.

While not shown, Carbon nanotube 310 may also be a “capped” nanotube. Acapped nanotube will experience functionalization preferentially alongits end caps, due to the increased energy due to the curvature in twodimensions.

Distal ends 314 and 316 therefore exhibit a relative charge differentfrom that of the middle of carbon nanotube 310. Depending on whatspecific functional group is adhered to distal ends 314 and 316, thisrelative charge can be either a partial delta negative charge or apartial delta positive charge. Other reasons that the functionalizedgroups cause preferential attachment of the nanotubes besides the chargeimbalance include, for example, but are not limited to polarity offunctional group, hydrogen bonding, and modification of Van der Waalsforces.

FIGS. 4-6 depict the fabrication of a printed circuit board according toan advantageous embodiment.

Referring now to FIG. 4, there is shown an electrically insulatingsubstrate 410. Electrically insulating substrate 410 is a base orsupporting material to which additional layers or materials are applied.Electrically insulating substrate 410 is, for example, but not limitedto, an epoxy substrate.

In these examples, signal-wiring conductors 412 and 414 can beselectively deposited into a connection pattern by a dry-film dielectricwith laser via process on selected surface portions of electricallyinsulating substrate 410, signal wiring conductors 412 and 414 are anelectrically conductive material. This material may be, for example, butnot limited to, copper, molybdenum, and tungsten. Each of the layers 412and 414 has a weight of, for example, about 0.5 ounces and a thicknessof, for example, about 18 micrometers.

Signal wiring conductors 412 and 414 can be patterned by directselective deposition, selective etching, or other suitable techniques.Signal wiring conductor 414 on the other side can be utilized as a powersupply layer. However, it should be clear to those skilled in the art,that signal wiring conductor 414 can also be patterned and segmentedinto a power mesh with signal pads distributed within the power mesh,but not necessarily connected to the power mesh.

As shown in FIG. 5, post 532 and post 534 are formed on substrate 510 ata location where a connection is to be established. Post 532 and post534 are fabricated at a predetermined distance from one another thatmatches a known length of a carbon nanotube that will be utilized tospan the distance between post 532 and post 534. The coupled carbonnanotube can form useful circuits when the substrate is designed withknowledge of nanotube length and desired electrical properties(chiralities).

While post 532 and post 534 are shown as being formed early in thefabrication process, it is appreciated that post 532 and post 534 can besimilarly fabricated at other points during fabrication of a printedcircuit board. Post 532 and post 534 can be formed, for example, but notlimited to, prior to deposition of any signal wiring connectors, afterdeposition of signal wiring connectors, and at any other point duringthe build up of various layers of the printed circuit boards.

Next, in FIG. 6, layer 618 of electrically insulating material,preferably a layer of photosensitive resin, is applied to cover thesignal-wiring conductors 612 in the first wiring layer, and thephotosensitive resin is then exposed and developed. The photosensitiveresin can be a negative type photosensitive epoxy resin applied to thesurface of the substrate by curtain coating, and then precured. Thephotosensitive resin is then developed with a developer. This developermay be, for example, a mixture of propylene carbonate, cyclohexanone,and gamma-butyrolactone.

After being developed, the surface of the epoxy resin layer 618 isroughened by etching with a solution of potassium permanganate, and isthen activated with a seeding chemical. This seeding chemical is asolution including colloidal tin and palladium in this illustrativeexample.

It is appreciated that signal wiring conductors 612 can be patterned byother methods known in the art, such as for example, by a dry-filmdielectric with laser via process by selective etching to form a secondwiring layer or wiring level which includes signal wiring conductors612. Additional layers may be added to one or both sides of the circuitboard in subsequent steps not shown here.

Referring now to FIG. 7, a functionalized carbon nanotube bath forcreating pathways is shown in accordance with an advantageousembodiment. Bath 700 contains functionalized carbon nanotubes 710 whichcan be carbon nanotube 310 of FIG. 3. Substrate 716 can be a printedcircuit board, such as the electrically insulating substrate 510 of FIG.5 that is formed into a printed circuit board as described in relationto FIG. 7.

Functionalized carbon nanotubes 710 are suspended in fluid matrix 714.Functionalized carbon nanotubes 710 have been filtered or otherwisesegregated such that each of functionalized carbon nanotubes 710 havesimilar chiralities and lengths. In one advantageous embodiment, each offunctionalized carbon nanotubes 710 is narrowly dispersed around a givenlength, such as, but not limited to 80+/−1 nanometers, 100+/−1nanometers, and 120+/−1 nanometers. In one advantageous embodiment, eachof functionalized carbon nanotubes 710 have similar chiral vectors (ornon-chiral vectors), such that each of functionalized carbon nanotubes710 within fluid matrix 714 have similar or identical indices (n, m).

It is appreciated that functional groups 712, attached to functionalizedcarbon nanotubes 710, may be present along the shaft of functionalizedcarbon nanotubes 710 in addition to the shown locations at distal endsof the functionalized carbon nanotubes 710. However, as shown in FIG. 3above, functional groups 712 preferentially adhere to distal ends offunctionalized carbon nanotubes 710. The relative concentration offunctional groups at distal ends of functionalized carbon nanotubes 710creates a relative charge at each of the distal ends of functionalizedcarbon nanotubes 710.

Bath 700 also contains fluid matrix 714. Fluid matrix 714 is a matrixcapable of suspending functionalized carbon nanotubes 710 in solution,without dissolving functionalized carbon nanotubes 710. In oneadvantageous embodiment, fluid matrix 714 is an aqueous solution.

Substrate 716 is submerged in fluid matrix 714. Substrate 716 includespost 718 and post 720. Post 718 and post 720 are fabricated on substrate716 such that the linear distance between the center of post 718 and thecenter of post 720 matches the known length of functionalized carbonnanotubes 710. Thus, in one advantageous embodiment, the linear distancebetween the center of post 718 and the center of post 720 can be one of80+/−1 nanometers, 100+/−1 nanometers, and 120+/−1 nanometers.

In one advantageous embodiment, post 718 and post 720 are functionalizedprior to immersion in fluid matrix 714.

Functional groups 712 of functionalized carbon nanotubes 710preferentially adhere to post 718 and post 720 rather than the remainderof substrate 716. Because the functionalized carbon nanotubes 710 havepreviously been filtered according to a desired size, functionalizedcarbon nanotubes 710 will energetically prefer to attach themselves in amanner that spans the linear distance between post 718 and post 720,thus creating an electrical pathway along functionalized carbonnanotubes 710.

Bath 700 also contains, or is functionally coupled to, agitation source722. Agitation source 722 is a source of disturbance to bath 700. Oncesubstrate 716 is submerged within bath 700, agitation source 722provides gentle agitation to fluid matrix 714.

The agitation of fluid matrix 714 provides the motion and energyrequired to remove nanotubes that may have adhered to post 718 or post720 along the shaft rather than at functional groups 712 offunctionalized carbon nanotubes 710. The agitation of fluid matrix 714further provides the necessary turbulence to impart motion to distalends of functionalized carbon nanotubes 710 that have adhered to one of,but not yet the other of, post 718 and post 720.

Motion of the ends distal from an attached end of functionalized carbonnanotubes 710 allows the distal end the opportunity to adhere to poststhat are located at the predetermined linear distance.

Referring now to FIG. 8, a completed circuit having a carbon nanotubepathway is shown according to an advantageous embodiment. Circuit 800 isa circuit formed from the preferential adherence of a functionalizedcarbon nanotube to posts within a bath, such as bath 700 of FIG. 7.

Substrate 810 can be a printed circuit board, such as the electricallyinsulating substrate 716 of FIG. 7 that is formed into a printed circuitboard as described in relation to FIG. 7. Substrate 810 includes post812 and post 814. Functionalized carbon nanotubes 816 spans the lineardistance between post 812 and post 814.

The self-assembly of circuit 800 results in functionalized carbonnanotubes 816 being anchored to both post 812 and post 814. Thus, thecoupled carbon nanotube can form useful circuits when the substrate isdesigned with knowledge of nanotube length and desired electricalproperties as determined by the chirality of the coupled carbonnanotubes.

After removing the substrate from the bath, the substrate can beannealed to remove functionalization from functionalized carbonnanotubes 816, as well as any functionalization on post 812 and post814. Annealing may also enhance electrical connections between posts 812and 814 to adhered carbon nanotubes.

In one advantageous embodiment, circuit 800 can be coated with a thinlayer of electrically insulating material. The insulating material alsoserves to hold functionalized carbon nanotubes 816 in place between post812 and post 814. Annealing may remove the functionalization that causedthe preferential adhesion. Therefore, the thin layer of electricallyinsulating material may be needed to preserve the physical connectionsbetween functionalized carbon nanotubes 816 and post 812, andfunctionalized carbon nanotubes 816 and post 814.

Referring now to FIG. 9, a flowchart of a method for assembling carbonnanotube electronics is shown in accordance with an advantageousembodiment.

Process 900 begins by providing a substrate having at least oneplurality of posts (step 910). The at least one plurality of posts arefabricated such that the center of the posts are located at apredetermined distance from one another. The predetermined distance ischosen to match the known length of a functionalized carbon nanotubethat will be used to span between the two posts.

Process 900 then exposes the substrate to a fluid matrix containingfunctionalized carbon nanotubes (step 920). The fluid matrix can be anaqueous bath or other liquid capable of suspending the functionalizedcarbon nanotubes. The functionalized carbon nanotubes within the fluidmatrix have been presorted based on both the chirality and the length ofthe functionalized carbon nanotubes. The chirality of the functionalizedcarbon nanotubes is chosen to impart desired electrical properties tothe carbon nanotube electronics. The length of the functionalized carbonnanotubes is chosen to match the predetermined distance between the twoposts of the substrate.

Process 900 then adheres a first end of the functionalized carbonnanotube to a first one of the at least one plurality of posts (step930). The first end of the nanotube is either distal end of the carbonnanotube having a relatively higher concentration of functional groupsthan does the shaft of the carbon nanotube. Due to the relative chargeof the distal end, the functionalized carbon nanotubes will selfassemble to the posts.

Process 900 then adheres a second end of the functionalized carbonnanotube to a second one of the at least one plurality of posts (step940), with the process terminating thereafter. Because each of thefunctionalized carbon nanotubes within the fluid matrix have the desiredchirality and length, the functionalized carbon nanotube will form apathway between the two posts. The pathway will have the desiredelectrical properties based on the chirality of the functionalizedcarbon nanotube.

Referring now to FIG. 10, a flowchart of the processing steps for theself-assembly of a carbon nanotube electronic circuit is shown accordingto an advantageous embodiment. Process 1000 is a physical process thatoccurs within a bath, such as bath 700 of FIG. 7.

Process 1000 begins by providing a substrate having at least two postsat a predetermined distance (step 1010). The substrate can be substrate716 of FIG. 7, and can be fabricated according to a method similar tothat described with regard to FIG. 7. The at least two posts at apredetermined distance are fabricated on the substrate at apredetermined distance chosen to match the length of carbon nanotubesthat will be used to span the predetermined distance between the centersof the two posts.

Optionally, the at least two posts at a predetermined distance can befunctionalized (step 1020). Functionalization of the posts may enhancethe affinity of nanotube ends to adhere to the posts.

Process 1000 continues by exposing the substrate to a bath containingfunctionalized carbon nanotubes (step 1030). The bath can be bath 700 ofFIG. 7. The functionalized carbon nanotubes can be carbon nanotube 310of FIG. 3. The functionalized carbon nanotubes in the bath have beenfiltered or otherwise segregated such that each of the functionalizedcarbon nanotubes has similar chiralities and lengths. In oneadvantageous embodiment, each of the functionalized carbon nanotubes isnarrowly dispersed around a given length, such as, but not limited to80+/−1 nanometers, 100+/−1 nanometers, and 120+/−1 nanometers. In oneadvantageous embodiment, each of the functionalized carbon nanotubeshave similar chiral vectors (or non-chiral vectors), such that each ofthe functionalized carbon nanotubes within the bath have similar oridentical indices (n, m).

The functional groups of the functionalized carbon nanotubespreferentially adhere to posts of the submerged substrate, rather thanthe remainder of substrate. Because the functionalized carbon nanotubeshave previously been filtered according to a desired size,functionalized carbon nanotubes will energetically prefer to attachthemselves in a manner that spans the linear distance between adjacentposts separated by the predetermined distance, thus creating anelectrical pathway along the functionalized carbon nanotube.

Process 1000 continues by agitating the bath (step 1040). Agitation ofthe bath provides the motion and energy required to remove nanotubesthat may have adhered to post 718 or post 720 of FIG. 7 along thenanotube shaft rather than at the distal ends of the functionalizedcarbon nanotubes. The agitation of fluid matrix further provides thenecessary turbulence to impart motion to distal ends of functionalizedcarbon nanotubes that have adhered to one of, but not yet the other of,adjacent posts separated by the predetermined distance. Motion of theends distal from an attached end of functionalized carbon nanotubesallows the distal end the opportunity to adhere to posts that arelocated at the predetermined linear distance.

The substrate is then removed from the bath (step 1050). Theself-assembly of the circuit results in functionalized carbon nanotubesbeing anchored to adjacent posts separated by the predetermineddistance. Thus, the coupled carbon nanotube can form useful circuitswhen the substrate is designed with knowledge of nanotube length anddesired electrical properties, as determined by the chirality of thefunctionalized carbon nanotube.

Optionally, after removing the substrate from the bath, the substratecan be annealed and coated with a thin layer of electrically insulatingmaterial (step 1060). Annealing the substrate can removefunctionalization from functionalized carbon nanotubes, as well as anyfunctionalization on posts. Annealing may also enhance electricalconnections between posts to the adhered carbon nanotubes. Theinsulating material also serves to hold the functionalized carbonnanotubes in place between the posts. Because annealing may remove thefunctionalization that caused the preferential adhesion, the thin layerof electrically insulating material may be needed to preserve thephysical connections between functionalized carbon nanotubes and theposts.

The advantageous embodiments provide a method and system for productionof nanotube-enabled circuits that do not rely on manual positioning ofthe nanotubes. Carbon nanotubes self-assemble on a metal-templatedsurface to form electrical connections including semiconductingconnections that define a circuit.

A fabricated substrate has at least one plurality of posts. Theplurality is fabricated such that the two posts are located at apredetermined distance from one another.

The substrate is exposed to a fluid matrix containing functionalizedcarbon nanotubes. The functionalized carbon nanotubes preferentiallyadhere to the plurality of posts rather than the remainder of thesubstrate. A connection between posts of the at least one plurality ofposts is induced by adhering a second end of the functionalized carbonnanotube to a second one of the at least one plurality of posts.

The lengths and chiralities of the functionalized carbon nanotubes arepreselected. The length of the functionalized carbon nanotubes matchesthe predetermined distance between the centers of posts of the pluralityof posts. The chirality of the functionalized carbon nanotubes isselected to impart the desired electrical properties to the createdcircuit.

Advantageous embodiments herein provide a system for production levelmanufacturing of nanotube-enabled circuits that do not rely on manualpositioning of the nanotubes. Producing carbon nanotube electronicsaccording to the disclosed method can substantially decrease productiontime and costs associated with the manufacture of carbon nanotubeelectronics, resulting in the feasibility of production scalemanufacturing of carbon nanotube-based electronics.

The description of the different advantageous embodiments has beenpresented for purposes of illustration and description, and is notintended to be exhaustive or limited to the embodiments in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art. Further, different advantageousembodiments may provide different advantages as compared to otheradvantageous embodiments. The embodiment or embodiments selected arechosen and described in order to best explain the principles of theembodiments, the practical application, and to enable others of ordinaryskill in the art to understand the disclosure for various embodimentswith various modifications as are suited to the particular usecontemplated.

What is claimed is:
 1. A system for assembling carbon nanotubeelectronics, the system comprising: a substrate, wherein the substratehas at least one plurality of posts, the at least one plurality of postsbeing fabricated at a predetermined distance from one another; a fluidmatrix containing functionalized carbon nanotubes, wherein thefunctionalized carbon nanotubes comprise a first end, a middle, and asecond end, wherein the first end and the second end have a relativeconcentration of functional groups different from that of the middlesuch that the functionalized carbon nanotubes exhibit relativeelectrical charges at the first end and the second end; an agitationsource, wherein providing agitation of the fluid matrix topreferentially adhere the first end of a functionalized carbon nanotubeto a first one of the at least one plurality of posts and adheres thesecond end of the functionalized carbon nanotube to a second one of theat least one plurality of posts due to the relative electrical chargesat the first end and the second end, wherein a connection is formedbetween the first one and the second one of the at least one pluralityof posts.
 2. The system of claim 1 further comprising: the fluid matrixcontaining the functionalized carbon nanotubes, wherein the fluid matrixcontains the functionalized carbon nanotubes having similar lengths andsimilar chiralities.
 3. The system of claim 2, wherein the similarlengths of the functionalized carbon nanotubes are selected tocorrespond to the predetermined distance between the first one and thesecond one of the at least one plurality of posts.
 4. The system ofclaim 2, wherein the similar lengths of the functionalized carbonnanotubes are selected from the group consisting of 80+/−1 nanometers,100+/−1 nanometers, and 120+/−1 nanometers.
 5. The system of claim 1,wherein the similar chiralities of the functionalized carbon nanotubesare selected based on desired electrical properties of thefunctionalized carbon nanotubes.
 6. The system of claim 5, wherein thedesired electrical properties of the functionalized carbon nanotubes isa conductance of the functionalized carbon nanotubes.
 7. The system ofclaim 5, wherein each of the functionalized carbon nanotubes havesimilar or identical chiral vectors.
 8. The system of claim 1, whereinthe fluid matrix is an aqueous matrix.
 9. The system of claim 1 furthercomprising: the agitation source, wherein the agitation source agitatesthe fluid matrix to induce removal of functionalized carbon nanotubesthat may have adhered to the first one and the second one of the atleast one plurality of posts along a shaft of the functionalized carbonnanotubes.
 10. The system of claim 1 further comprising: the agitationsource, wherein the agitation source agitates the fluid matrix to impartmotion to distal ends of functionalized carbon nanotubes that haveadhered to one of, but not yet the other of, the first one and thesecond one of the at least one plurality of posts.
 11. The system ofclaim 1, wherein the functionalized carbon nanotubes comprise carboxylicacid functional groups.
 12. The system of claim 1 further comprising: aheat source, wherein the heat source anneals the substrate to removefunctional groups from the functionalized carbon nanotubes.
 13. Thesystem of claim 12 further comprising: the heat source, wherein the heatsource anneals the substrate to remove functional groups from the firstone and the second one of the at least one plurality of posts.
 14. Thesystem of claim 1 further comprising: an electrically insulatingmaterial, wherein the electrically insulating material comprises acoating applied to the substrate.
 15. The system of claim 13, whereinthe electrically insulating material comprises a layer of photosensitiveresin applied to cover the connection formed between the first one andthe second one of the at least one plurality of posts.
 16. The system ofclaim 1, wherein the substrate is a printed circuit board.
 17. Thesystem of claim 1, wherein the functionalized carbon nanotubes areselected from the group consisting of open ended carbon nanotubes andcapped carbon nanotubes.
 18. The system of claim 1, wherein the firstone and the second one of the at least one plurality of posts arefunctionalized prior to immersion in the fluid matrix.
 19. The system ofclaim 1, wherein the connection formed by the functionalized carbonnanotube spans a linear distance between the first one and the secondone of the at least one plurality of posts.